This application relates to compensation for optical dispersion, and more specifically, to techniques and systems for reducing chromatic dispersion in optical media such as optic fiber links.
Many optical fibers and other optical transmission media can exhibit chromatic dispersion when different spectral components at different wavelengths in an optical signal travel at different speeds. An optical pulse, which comprises different optical spectral components, therefore, can be broadened or distorted in shape after propagation through a distance in such a dispersive optical medium. This dispersion effect can be undesirable and even adverse for certain applications such as optical communication systems where information is encoded, processed, and transmitted through optical pulses. The pulse broadening caused by the dispersion can limit the transmission bit rate, the transmission bandwidth, and other performance factors of the optical communication systems.
One way to mitigate the chromatic dispersion in dispersive optical fibers and other optical transmission media is dispersion compensation which introduces dispersion in an optical signal to negate the dispersion accumulated in that optical signal. In a wavelength-division multiplexed (WDM) optical systems, multiple WDM optical channels at different wavelengths are simultaneously transmitted through a fiber system. Since the dispersion in different WDM channels may be different, it may be desirable to provide different amounts of dispersion compensation to different WDM channels at the same time. In addition, since the dispersion in the WDM channels may vary over time, it may also be desirable to adjust the dispersion compensation in time for different WDM channels.
One embodiment of the present disclosure includes a fiber grating formed in a fiber and configured to have a spatial grating pattern that changes nonlinearly along the fiber to exhibit up to at least a third-order nonlinear dispersion effect so as to produce a tunable dispersion slope. A grating control unit may be coupled to the fiber grating and is operable to adjust a grating parameter of the fiber grating to tune both dispersion and dispersion slope produced by the fiber grating.